<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>计算器</title>
    <style>

        *{
            border:none;
            font-family:'Open Sans',sans-serif;
            margin: 0;
            padding: 0;
        }
        .center{
            background-color: #ffffff;
            border-radius: 50%;
            height: 600px;
            margin:auto;
            width: 600px;
        }
        h1{
            color: #495678;
            font-size: 30px;
            margin-top: 20px;
            padding-top: 50px;
            display: block;
            text-align: center;
            text-decoration: none;
        }
        form{
            background-color: #495678;
            box-shadow:4px 4px #3d4a65;
            margin: 40px auto;
            padding:40px 0 30px 40px;
            width: 280px;
        }
        .btn{
            outline: none;
            cursor: pointer;
            font-size: 20px;
            height: 45px;
            margin: 5px 0 5px 10px;
            width: 45px;
        }
        .btn:first-child{
            margin: 5px 0 5px 10px;
        }
        .btn, #display, form{
            border-radius: 25px;
        }
        #display{
            outline:none;
            background-color: #98d1d3;
            box-shadow: inset 6px 6px 0 #3facc0;
            color: #dededc;
            font-size: 20px;
            height: 47px;
            text-align: right;
            width: 165px;
            padding-right: 10px;
            margin-left: 10px;
        }
        .number{
            background-color: #72778b;
            box-shadow: 0 5px #5f6680;
            color: #dededc;
        }
        .number:active{
            box-shadow: 0 2px #5f6680;
            transform: translateY(2px);
        }
        .operator{
            background-color: #dededc;
            box-shadow: 0 5px #bebebe;
            color: #72778b;
        }
        .operator:active{
            box-shadow: 0 2px #bebebe;
            transform: translateY(2px);
        }
        .other{
            background-color: #e3844c;
            box-shadow: 0 5px #e76a3d;
            color: #dededc;
        }
        .other:active{
            box-shadow: 0 2px #e76a3d;
            transform: translateY(2px);
        }
    </style>
</head>
<body>
<div class="center">
    <h1>HTML,CSS,JAVASCRIPT计算器</h1>
    <form name="calculator">
        <input type="button" id="clear" class="btn other" value="c">
        <input type="text" id="display">
        <br>
        <input type="button" class="btn number" value="7" onclick="get(this.value)">
        <input type="button" class="btn number" value="8" onclick="get(this.value)">
        <input type="button" class="btn number" value="9" onclick="get(this.value)">
        <input type="button" class="btn operator" value="+" onclick="get(this.value)">
        <br>
        <input type="button" class="btn number" value="4" onclick="get(this.value)">
        <input type="button" class="btn number" value="5" onclick="get(this.value)">
        <input type="button" class="btn number" value="6" onclick="get(this.value)">
        <input type="button" class="btn operator" value="*" onclick="get(this.value)">
        <br>
        <input type="button" class="btn number" value="1" onclick="get(this.value)">
        <input type="button" class="btn number" value="2" onclick="get(this.value)">
        <input type="button" class="btn number" value="3" onclick="get(this.value)">
        <input type="button" class="btn operator" value="-" onclick="get(this.value)">
        <br>
        <input type="button" class="btn number" value="0" onclick="get(this.value)">
        <input type="button" class="btn operator" value="." onclick="get(this.value)">
        <input type="button" class="btn operator" value="/" onclick="get(this.value)">
        <input type="button" class="btn other" value="=" onclick="calculates()">
    </form>
</div>


<script>

    document.getElementById('clear').addEventListener('click',function () {
        document.getElementById('display').value = '';
    })
    function get (value) {
        document.getElementById('display').value += value;
    }
    function calculates () {
        var result = 0;
        result = document.getElementById('display').value;
        document.getElementById("display").value = "";
        document.getElementById("display").value = eval(result);
    }
</script>
</body>
</html>